Various types of tin dioxide coated electrodes are known.
U.S. Pat. No. 3,627,669 describes an electrode comprising a valve metal substrate having a surface coating consisting essentially of a semiconductive mixture of tin dioxide and antimony trioxide. A solid-solution type surface coating comprising titanium dioxide, ruthenium dioxide and tin dioxide is described in U.S. Pat. No. 3,776,834 and a multi-component coating containing tin dioxide, antimoy trioxide, a valve metal oxide and a platinum group metal oxide is disclosed in U.S. Pat. No. 3,875,043.
Another type of coating, described in U.S. Pat. No. 3,882,002 uses tin dioxide as an intermediate layer, over which a layer of a noble metal or a noble metal oxide is deposited. Finally, U.S. Pat. No. 4,028,215 describes an electrode in which a semiconductive layer of tin dioxide/antimony trioxide is present as an intermediate layer and is covered by a top coating consisting essentially of manganese dioxide.